The present invention is directed to a micromechanically manufacturable capacitive pressure sensor.
Capacitive pressure sensors are employed for measuring absolute pressure. A closed chamber with a reference pressure is closed off by an elastic membrane that is exposed to an external pressure. Together with the opposite side of this chamber, the electrically conductive membrane forms a plate capacitor. The membrane is deformed due to the pressure difference between the external pressure and the internal reference pressure. The capacitance of this capacitor changes due to the altered distance between the membrane and the back side of the chamber acting as a cooperating electrode. The external pressure can be determined from this change in capacitance.
U.S. Pat. No. 5,095,401 incorporated herein by Paul M. Zavracky et al. discloses pressure sensors on a SOI substrate wherein a cavity is produced such that a region of silicon oxide produced with a LOCOS technique is removed through small openings in a layer applied thereon. These openings are subsequently closed by oxidation of the adjoining silicon, or by applying a further layer of silicon nitride, polysilicon or the like. This Letters Patent also discloses the employment of the manufacturing method disclosed therein for the manufacture of capacitive measuring pressure sensors. A crystallized silicon layer is a component part of the membrane of this pressure sensor, this crystallized silicon layer being employed outside of the pressure sensor for the integration of electronic components and being employed in the region of the membrane for designing piezo resistors.